Oxidation of alcohols is a fundamental transformation related to our daily life. Traditional approaches with at least one stoichiometric amount of oxidants are expensive and cause serious environmental burdens. There are many reports on the aerobic oxidation of simple alcohols such as alkyl or phenyl carbinols and allylic alcohols, which used oxygen or air as the environmentally benign oxidant forming water as the only by-product. However, no such protocol has been reported for allenols and propargylic alcohols. Thus, it still highly desirable to develop efficient room temperature oxidations of alcohols with a wide scope including allenols and propargylic alcohols. In this paper, an efficient and clean aerobic oxidation of so far the widest spectrum of alcohols using 1 atm of oxygen or air, producing aldehydes/ketones at room temperature in fairly high isolated yields mostly within a couple of hours is described. It is interesting to observe that the reaction has been efficiently expedited by a catalytic amount of sodium chloride in easily recoverable 1,2-dichloroethane. A mechanism involving NO and NO 2 has been proposed based on the results of the control experiments and GC-MS studies of the in-situ formed gas phase of the reaction mixture.

A new reaction for the rhodium‐catalyzed geminal‐difunctionalization‐based fluorination is presented. The substrates are aromatic and aliphatic diazocarbonyl compounds. As the fluorine source a stable and easily accessible benziodoxole reagent was used. A variety of alcohol, phenol, and carboxylic acid reagents were employed to introduce the second functionality. The reaction was extended to trifluoromethylation using a benziodoxolon reagent. The fluorination and trifluoromethylation reactions probably proceed by a rhodium‐containing onium ylide type intermediate, which is trapped by either the F or CF3 electrophiles.

Application of a fluoroiodine analogue of the Togni reagent was studied in fluorocyclization reactions. In the presence of a transition-metal catalyst the applied fluoroiodine reagent can be used for aminofluorination, oxyfluorination, and carbofluorination reactions. The described procedure has a very broad synthetic scope for preparation of functionalized hetero- and isocyclic compounds having a tertiary fluorine substituent.

Activation of carbon dioxide and converting it into useful chemical feedstock have attracted much attention owing to the fact that CO 2 is abundant, inexpensive, nontoxic, and environmentally benign.[1] However, the challenges still to be overcome are its lack of thermodynamic and kinetic stability. For the reaction of allylic tin species, [2] aryl boronates, and limited examples of 1-alkenyl boronates, [3] aryl or alkyl zinc substrates [4,5] can react with carbon dioxide, usually under palladium, nickel, copper, or rhodium catalysis [Scheme 1, Eq. (1)]. In addition, a stoichiometric amount of Ni or Ti reagents have been used to mediate the reaction of CO 2 with alkene, [6] diene, [7] alkyne, [8] or allene [9] substrates to form fivemembered metallaoxacyclic intermediates A, which may undergo further reactions to afford carboxylation products [Scheme 1, Eq. (2)]. There are very limited reports on the catalytic reactions of alkyne [10] or allene [11] substrates involving A-type intermediate using 20 mol % of [Ni(cod) 2 ] and 10 equivalents of 1,8-diazabicyclo[5.4.0]undec-7-ene.Furthermore, there are a few reports on substituted alkynes that can undergo a stereoselective titanium-or rhodium-catalyzed syn-hydrozincation [12,13] or rhodium-or nickel-catalyzed carbozincation [13,14] reaction [Scheme 1, Eq. (3)]. With this notion in mind, we envisioned that organozinc reagents generated in situ from hydro-or carbozincation of unsaturated hydrocarbon species may react with CO 2 to afford the corresponding carboxylic acids in a convenient manner [Scheme 1, Eq. (3)]. Rovis and co-workers reported the hydrozincation/carboxylation of styrenes with [Ni(acac) 2 ] (10 mol %; acac = acetylacetonate) and Cs 2 CO 3 (20 mol %).[15] Takaya and Iwasawa reported such a hydrocarboxylation of allene with 1-2.5 mol % of a silyl pincer-type palladium complex.[16] However, it should be noted that both reports involve the reaction of very reactive allylic or benzylic metallic species with CO 2 . So far, there are no such reports on alkyne substrates; the challenge here would be the lower reactivity of the 1-alkenylic zinc generated in situ towards CO 2 [17] and the regioselectivity of the alkynes. Herein, we report the concise highly regio-and stereoselective three-component nickel-catalyzed (1-3 mol %) synhydrocarboxylation of alkynes [11,12] with diethyl zinc and the subsequent efficient reaction with carbon dioxide mediated by CsF to afford stereodefined and synthetically useful 2-alkenoic acids. This reaction has been applied to the highly regio-and stereoselective synthesis of 3-alkylideneoxindole [18] and a-alkylidene-g-butyrolactam.[19]Initially, diphenylacetylene (1 a) was treated with CO 2 in the presence of 10 mol % of [Ni(cod) 2 ], 20 mol % of PCy 3 , and 3 equivalents of ZnEt 2 . Pleasingly, 10 % of the expected synhydrocarboxylation product, that is, (E)-2,3-diphenylacrylic acid 2 a, was formed together with 25 % of the hydrolysis product 4 a (Table 1, entry 1). Various bases were then screened with no obvious improvem...

CuBr and ZnI(2) have been developed as catalysts or subcatalysts for the efficient asymmetric synthesis of axially chiral allenols with up to 97% ee from readily available propargylic alcohols, aliphatic or aromatic aldehyde, pyrrolidine, and commerically available ligands. The alcohol unit in the terminal alkynes plays a very important role for ensuring high enantioselectivity via coordination.